<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style type="text/css">
        *{
            padding:0;
            margin:0;
        }
        body{
            font-size: 14px;
            font-family: "微软雅黑";
            background: url('img/people.jpg') no-repeat;
            background-size: 100%;
            height: 100%;
            width: 100px;
        }
        
        a {
            text-decoration: none;
            color: #ffffff;
        }
        ul li {
            list-style: none;
        }
        .over{
            width: 100%;
            height: 100%;
        }
        #formbox{

        }
    </style>
</head>
<body>
    <div class="over">
         <div id="formbox">
             <input type="text" id="username"/>
             <input type="text" id="password"/>
             <input type="button" id="login" value="登录">
         </div>
    </div>

    <script src="jquery-1.12.2.min.js"></script>
    <!-- 最好边写边测试 -->
    <script type="text/javascript">
        $(function(){
            $("#login").on("click",function(){
                var username = $("#username").val();
                var password = $("#password").val();

                if(!username){
                    alert("请输入密码");
                    return;
                }

                if(!password){
                    alert("请输入密码");
                    return;
                }

                $.ajax({
                    type : "post",
                    data : params,
                    url : "login.jsp",
                    success:function(data){

                    }
                });
            });
        });

    </script>
</body>
</html>